An evaluation of temporal changes in the trophic structure of Gulf of Maine ecosystem

The Gulf of Maine (GOM) ecosystem has experienced significant changes in the last few decades with a great increase in the American lobster Homarus americanus population and substantial reduction in some groundfish populations like Atlantic cod Gadus morhua. This study evaluated and compared the energy flows and trophic structures of the GOM ecosystem in the mid-2000s and mid-2010s. Following an early study, two mass-balance ecosystem models, each of which include 25 functional groups, were updated for the mid-2000s and mid-2010s using Ecopath. Fishing efforts were used as forcing drivers to simulate the variation of the GOM ecosystem in the mid-2000s to mid-2010s. Similar to the GOM ecosystem from the 1980s to 1990s found in a previous study, dominant species in both the mid-2000s and mid-2010s ecosystems were transferred from top predators to crustacean species in the last decade. However, food web structure of the GOM ecosystem became more complex, stable, and flexible to perturbations, indicating that the GOM ecosystem is moving toward a more mature stage. Simulation results indicated that fishing activities were considered to be the main driver to the variations dynamics of most species in the GOM ecosystem, while some species like Atlantic herring Clupea harengus might also suffer from changes in environmental conditions. This study provides a comprehensive overview on the changes in the GOM ecosystem in the last two decades.